Method for the production of a fiber web

ABSTRACT

A method for the production of a fiber web from a fiber stock suspension including a filler, including the steps of: selecting at least one size of at least one filler particles for a predetermined color of the fiber web, including at least one filler particles in the filler, adding at least one filler including at least one filler particles of at least one size in the fiber stock suspension and producing the fiber web in the predetermined color.

This is a continuation in part of U.S. patent application Ser. No.10/242,821, entitled “METHOD FOR THE PRODUCTION OF A FIBER WEB”, filedSep. 13, 2002.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for the production of a fiberweb, specifically a paper or cardboard web, from a fiber stocksuspension.

2. Description of the Related Art

The current trend is to produce paper having brightness values that areas high as possible. These brightness values may be achieved byintroducing fillers such as calcium carbonate, or ground calciumcarbonate into the fiber stock suspension.

The loading with an additive, i.e. a filler, may occur for examplethrough a chemical precipitation reaction, that is specifically througha so-called “fiber loading™” process, such as described in the prior artdocumentation U.S. Pat. No. 5,223,090 and U.S. Pat. No. 6,355,138, amongothers. During such a “fiber loading™” process at least one additive,specifically a filler, is deposited on the moistened fiber surfaces ofthe fiber material. The fibers may, for example, be loaded with calciumcarbonate. To this end, calcium oxide and/or calcium hydroxide are addedto the moist disintegrated fiber material in such a manner, whereby atleast a portion of these additives associates with the water that iscontained in the fiber material. The fiber material treated in thismanner is subsequently supplied with carbon dioxide.

What is needed in the art is a method for loading a fiber web with anadditive to improve brightness and that would provide as simple and asreliable a method as possible for the production of fiber webs invarious colors.

SUMMARY OF THE INVENTION

The present invention provides a method for the production of a fiberweb, specifically a paper or cardboard web, from a fiber stocksuspension containing a filler, whereby the size of the filler particlesis selected with the particular objective of producing a fiber web of apredetermined color.

The present invention comprises, in one form thereof, a method for theproduction of a fiber web from a fiber stock suspension including afiller, including the steps of: selecting at least one size of at leastone filler particles for a predetermined color of the fiber web,including at least one filler particles in the filler, adding at leastone filler including at least one filler particles of at least one sizein the fiber stock suspension and producing the fiber web in thepredetermined color.

An advantage of the present invention is a simple and reliable methodfor the production of fiber webs in various colors.

Another advantage is the production of fiber webs in various colors withimproved brightness.

Yet another advantage is the fact that the dispersion and reflection oflight is dependent upon the respective particle size.

DETAILED DESCRIPTION OF THE INVENTION

According to a preferred practical arrangement of the method accordingto the present invention, filler particles of one and the same size areutilized in order to produce the color of the fiber web. In thisinstance the color produced by the relevant particle size constitutesthe actual color of the fiber web that is visible from the surface.

According to an advantageous alternative arrangement, filler particlesof varying sizes are utilized whereby the different particle sizes areselected so that the color of the fiber web results from the differentcolors produced by the different particle sizes. The visible exteriorcolor of the fiber web therefore, results from two or more primarycolors produced by the respective particle sizes. Specifically threedifferent particle sizes may be used in this process, and the differentparticle sizes selected so that three primary colors are produced fromwhich the color of the fiber web results. The utilized volume of fillersof a specific particle size is controlled and/or adjusted to advantage.Specifically, the ratio of the utilized filler volumes of varyingparticle sizes can also be controlled and/or adjusted.

According to a functional practical arrangement of the method inaccordance with the present invention, the throughput of at least onepartial suspension stream containing filler of a certain particle sizeis controlled and/or adjusted. Specifically, the relationship of thethroughputs of two or more partial suspension streams containing fillersof varying particle sizes can also be controlled and/or adjusted.

According to an effective arrangement of the method in accordance withthe present invention, several fiber webs containing fillers of varyingparticle sizes are produced, and the varying particle sizes selectedwith the objective that the color of the finished fiber web will be aresult of the different colors produced by the varying particle sizes.Specifically, several headboxes may be used whose partial suspensionstreams contain filler of varying particle sizes. The headboxthroughputs and/or the filler content of the partial suspension streamscan be controlled and/or adjusted.

Advantageously three headboxes are utilized in order to produce threeprimary colors through three different filler particle sizes, resultingin the color of the fiber web.

In order to produce the filler particles, a chemical precipitationreaction is effectively triggered and/or a refining process carried out.Basically however, any other desired manufacturing process is alsofeasible. The filler can consist specifically of one or several of thefollowing materials: precipitator, synthetic material, calciumcarbonate, talc, TiO₂, silica and/or similar materials.

According to a preferred practical arrangement of the method inaccordance to the present invention, the fiber suspension is loaded withfiller through a chemical precipitation reaction, whereby especiallycrystalline precipitator particles are produced. The precipitator mayfor example be calcium carbonate.

It is also particularly advantageous if calcium oxide and/or calciumhydroxide is added to the fiber stock suspension for the purpose ofloading the fibers, and if the precipitation is triggered by supplyingcarbon dioxide to the fiber suspension.

When loading the fibers with filler, calcium carbonate (CaCO₃) can forexample be deposited at the moistened fiber surfaces by adding calciumoxide (CaO) and/or calcium hydroxide (Ca(OH)₂) to the moist fibermaterial, whereby at least a portion of this can associate with thewater of the fiber volume. Carbon dioxide (CO₂) can then be introducedto the treated fiber material.

The term “moistened fiber surfaces” may encompass all moistened surfacesof the individual fibers. This specifically also encompasses theinstance where the fibers are loaded with calcium carbonate or any otherdesired precipitator on their outer surface as well as in their interior(lumen).

Accordingly, the fibers may for example be loaded with the fillercalcium carbonate, whereby the deposit onto the moistened fiber surfacesoccurs through a so-called “fiber loading™” process, as described in theprior art documents U.S. Pat. No. 5,223,090 and U.S. Pat. No. 6,355,138.In this “fiber loading™” process the carbon dioxide reacts, for example,with the calcium hydroxide to water and calcium carbonate. The calciumhydroxide may be introduced to the fiber stock suspension in liquid orin dry form.

Specifically a refining process can produce the appropriate particlesize.

A preferred practical arrangement of the method according to the presentinvention distinguishes itself in that the fiber stock suspension isloaded with filler through a chemical reaction and in that the fibersthat are loaded with filler are refined in order to produce anappropriate filler particle size.

In certain instances it may be advantageous if a chemical color is usedadditionally as a brightener. Production of paper in different colors istherefore possible for example, by utilizing particles whose size isselected so that for the production of a certain color in the finishedpaper, a respective color of the visible light is reflected.

The particles that are present in the finished product may for examplebe produced by a precipitation reaction, by refining and/or by anotherproduction process. The utilized material may, for example, be aprecipitator or a synthetic material, calcium carbonate, talc, TiO₂,silica and/or a similar material.

The particle size is fundamental to achieving optimum opacity as well asthe desired color. A high opacity or brightness is achieved when thecolor spectrum of the visible light is well dispersed. If the entirecolor spectrum is absorbed, the resulting color will be black. If thefiller particle size is below a value of specifically 0.2 to 0.5 μm, thetendency is toward achieving a higher transparency and a higher gloss.

In order to obtain colored paper, the particle size of the filler mustbe in a range in which only one color of the visible light is reflected.The paper then possesses a resulting color that is complimentary to theabsorbed color. If for example, a filler particle absorbs the colorblue, the resulting color will be yellow. If a filler particle isproduced which absorbs only one color, then the paper will be in thecomplimentary color.

If the paper contains two filler particles, or more precisely two fillertypes that differ in their particle size, where the one particle or theone filler type absorbs for example the color blue and the other oneabsorbs the color yellow, then the resulting paper color will be green.

Obviously, any other examples of the method according to the inventionwould also be feasible.

Viewed physically, color is an optical phenomenon that captures acertain frequency range of the visible light. Light is known to be aform of electromagnetic radiation that transmits at the velocity oflight. Color is a subjective immaterial sensation that occurs when lightenters the eyes.

The visible spectrum of light has a wavelength of 400 to 800 nm, wherebycertain color impressions occur at certain wavelength ranges, asindicated in the table below: Wave length range Color impression 800-605red 605-595 orange 595-580 yellow 580-560 yellow-green 560-500 green500-490 bluish-green 490-480 green-blue 480-435 blue 435-400 violet

White light is not a color in the physical sense. It does however, showa mixture of all above referenced colors. If one color of the visiblelight is filtered out, the complimentary color remains as indicated inthe table below: Filtered out color Complimentary color Blue Yellow RedCyan Green Magenta

Basically, a color can also be produced through a combination of variouscolors, as indicated in the following examples: Resulting Color Originalcolors White = Red + Green + Blue Yellow = Red + Green Magenta = Red +Blue Cyan = Green + Blue

Basically, color can originate in various ways. Chemical colors forexample, find their origin in colored substances, atoms and especiallyin molecules that selectively absorb the sources of light, whereby thecolor of the atoms or molecules is complementary to the filtered outlight. Structural colors result through refraction, reflection,dispersion and interference.

For the production of colors according to the present invention throughcorrelative particle sizes, and particularly for utilization of theso-called “fiber loading™” process the dispersion and reflection is ofparticular interest. In contrast, refraction is used primarily inoptical devices. Interference or superposition of waves is also excludedin this instance.

Light is dispersed on very small particles such as for example dust, inother words, it is reflected in all directions. The dispersion effectdepends greatly on the wavelength. Higher frequencies with shorterwavelengths therefore, are dispersed more strongly. Blue light forexample, is dispersed approximately ten times more strongly than redlight.

In the case of a medium consisting of extremely small particles, theblue light is dispersed or filtered out first, and then the yellowlight. A white light beam changes its color from white to yellow andthen to red.

In the application of, for example, a paper containing fillers, whitepaper is created when the filler particles reflect the entire spectrumcolors, resulting in white light. White paper therefore is created ifthe filler particles are of appropriately different sizes. Transparentpaper is created when the light can pass unimpeded through the paper,that is, if light is possibly reflected but, however, no light sourcesof certain size are filtered out. If a filler particle is produced thatfilters out a certain wavelength of the visible light, then the paperwill appear in the complimentary color. If for example, blue is filteredout, then the paper will appear in the color yellow.

If for example different layers are contained in a certain paper type,that respectively filter out a certain wavelength of light, and that areadditively mixed, then basically, any desired paper color can beselected. In one example of the method according to the presentinvention, the coating processes that were hitherto used for coloring ofthe paper are superfluous. A pre-condition for this is that the fillerpigments only filter out the respective color, irrespective of whetherthey were produced by the so-called “fiber loading™” process or byanother manufacturing process. This may signify for example, that therespective headbox must be controlled and/or adjusted to an optimum withregard to its throughput and with regard to the filler content. Thissignifies that, for example, three headboxes with fillers of differentparticle sizes containing a respective primary color may be utilized, inorder to cover the entire color range.

A possible gray cast in the produced paper colors may be avoided byadditionally using chemical colors in lower volumes as brighteningagents.

Basically, other desired arrangements of the method according to theinvention are also feasible.

The necessary filler particle size ranges are in the range of thevisible wavelength, i.e., in the range of nanometers (nm), and morespecifically in the bandwidth ranges given in the table above. Aspreviously mentioned, there is a correlative relationship between theparticle size and color of the paper, or between the combination ofparticle sizes and resulting paper color. For a predetermined color ofthe fiber web, the particle size is selected to be in the wavelengthrange of that predetermined color. As given in the table above, awavelength range of light provides a given color impression, such as abandwidth of 800 nm-605 nm produces a color impression of red.Therefore, filler particles on the order of 800 nm-605 nm are added fora red fiber web. For a combination color such as yellow, fillerparticles corresponding to red and green color impressions, i.e., 800nm-605 nm filler particle sizes and 560 nm-500 nm filler particle sizesare added to the fiber web. As is known in the optical and color arts,even highly coherent light sources, such as lasers, which produce a“single” color light have a bandwidth but still appear as a singlecolor, such as red in the case of a HeNe laser. Therefore, it is notnecessary to provide a single filler particle size for a resulting colorimpression; instead, particle sizes which are in the wavelengthbandwidth of a color impression can be produced that result in theresultant color impression of the fiber web.

Filler particles can be produced in the appropriate size ranges using achemical slaking process as is known. For example, a common filler iscalcium hydroxide. The slaking process converts limestone (CaCO₃), withthe addition of heat, to calcium oxide and carbon dioxide (CaO+CO₂).However, calcium oxide (CaO) can be unstable in the presence of moistureand CO₂. A more stable form of lime is calcium hydroxide (Ca(OH)₂) whichcan be produced by combining the calcium oxide (CaO) with water H₂O toproduce calcium hydroxide (Ca(OH)₂)+heat. The chemical slaking processcan be supported by beating and/or producing high shear forces whenproducing the calcium hydroxide lime to reduce the filler particle size.Further, grinding of the filler particles can reduce their size, andother refining such as filtering or screening can produce particle sizesin a range corresponding to the wavelength bandwidth of a given colorimpression. As previously mentioned, when loading the fibers withfiller, calcium carbonate (CaCO₃) can for example be deposited at themoistened fiber surfaces by adding calcium oxide (CaO) and/or calciumhydroxide (Ca(OH)₂) to the moist fiber material, whereby at least aportion of this can associate with the water of the fiber volume. Carbondioxide (CO₂) can then be introduced to the treated fiber material. Thefiller can include one or several of the following materials:precipitator, synthetic material, calcium carbonate, talc, TiO2, silicaand/or similar materials.

The fiber loading process can include parameters to change for steeringthe size of the filler particles. For example, the present invention caninclude a method for a production of a fiber web from a fiber stocksuspension including a filler, including the steps of: loading at leastone filler including a plurality of filler particles in the fiber stocksuspension; and refining the fiber stock suspension after the loadingstep to produce the plurality of filler particles in a predeterminedsize range. This method can further include the step of producing thefiber web in a predetermined color corresponding to the predeterminedsize range. The refining step can be a beating operation, for example.

As mentioned above, a high opacity or brightness of a fiber web isachieved when the color spectrum of the visible light is well dispersed.To that end, dispersing chemicals can be added to the fiber web. Thepresent invention therefore includes a method for a production of afiber web from a fiber stock suspension including a filler, includingthe steps of: loading at least one filler including a plurality offiller particles in the fiber stock suspension; and adding at least onedispersing chemical to the fiber stock suspension. The method canfurther include the steps of producing the fiber web, and improving atleast one of an opacity of the fiber web and a brightness of the fiberweb.

While this invention has been described as having a preferred design,the present invention can be further modified within the spirit andscope of this disclosure. This application is therefore intended tocover any variations, uses, or adaptations of the invention using itsgeneral principles. Further, this application is intended to cover suchdepartures from the present disclosure as come within known or customarypractice in the art to which this invention pertains and which fallwithin the limits of the appended claims.

1. A method for the production of a fiber web from a fiber stocksuspension including a filler, comprising the steps of: selecting atleast one size of at least one filler particles for a predeterminedcolor of the fiber web; including at least one said filler particles inthe filler; adding at least one filler including at least one saidfiller particles of at least one said size in the fiber stocksuspension; and producing the fiber web in said predetermined color. 2.The method of claim 1, wherein said method is carried out using a singlesaid size of said filler particles.
 3. The method of claim 1, whereinsaid method is carried out using a plurality of said sizes of saidfiller particles, said plurality of said sizes produces a plurality ofcolors, said predetermined color of the fiber web resulting from saidplurality of colors.
 4. The method of claim 3, wherein said method iscarried out using three different said sizes of said filler particles toproduce three primary colors which results in said predetermined colorof the fiber web.
 5. The method of claim 1, wherein said method iscarried out using at least one volume of said filler particles, eachdistinct said volume corresponding to a distinct said size, at least onesaid volume is at least one of controlled and adjusted.
 6. The method ofclaim 5, wherein said method is carried out using at least one ratio ofat least one said volumes, said ratio is at least one of controlled andadjusted.
 7. The method of claim 1, wherein said method is carried outusing the fiber stock suspension including at least one partialsuspension stream, each distinct said partial suspension streamcorresponding to a distinct said size of said filler particles and athroughput, at least one said throughput is at least one of controlledand adjusted.
 8. The method of claim 7, wherein said method is carriedout using at least one ratio of a plurality of said throughputs, saidratio is at least one of controlled and adjusted.
 9. The method of claim7, wherein said method is carried out using a plurality of headboxes,each said headbox including at least one said partial suspension streamand a headbox throughput, at least one said partial suspension streamincluding a content of said filler of varying said sizes of said fillerparticles, at least one of said headbox throughput and said content areat least one of controlled and adjusted.
 10. The method of claim 9,wherein said method is carried out using three said headboxes to producethree primary colors through three distinct said sizes of said fillerparticles which results in said predetermined color of the fiber web.11. The method of claim 1, wherein said method is carried out producinga finished fiber web including a plurality of the fiber webs, each ofthe fiber webs including said fillers of varying said sizes of saidfiller particles, each said size of said filler particles associatedwith a different color, said sizes selected to produce said finishedfiber web in said predetermined color, resulting from said differentcolors produced by said sizes of said filler particles.
 12. The methodof claim 1, further including the step of producing at least one saidfiller particles by at least one of triggering a chemical precipitationreaction and a refining process, said producing at least one said fillerparticles step is prior to said including step.
 13. The method of claim1, wherein said method is carried out with said filler including atleast one of precipitator, synthetic material, calcium carbonate, talc,TiO₂, silica and similar materials.
 14. The method of claim 1, whereinsaid method is carried out by loading the fiber suspension with saidfiller through a chemical precipitation reaction.
 15. The method ofclaim 14, wherein said chemical precipitation reaction produces acrystalline precipitator particles.
 16. The method of claim 15, whereinsaid precipitator is calcium carbonate.
 17. The method of claim 16,further including the steps of adding at least one of calcium oxide andcalcium hydroxide to the fiber stock suspension, the fiber stocksuspension including fibers, the fibers are loaded by said adding step;and supplying carbon dioxide to the fiber suspension thereby triggeringsaid chemical precipitation reaction.
 18. The method of claim 1, furtherincluding a refining process step to produce a predetermined said sizeof said filler particles.
 19. The method of claim 1, further includingthe steps of loading the fiber stock suspension with said filler througha chemical reaction, the fiber stock suspension including fibers whichare loaded with said filler; and refining the fibers thereby producing apredetermined said size of said filler particles.
 20. The method ofclaim 1, wherein said method is carried out using a chemical color as abrightner.
 21. A method for a production of a fiber web from a fiberstock suspension including a filler, comprising the steps of:. loadingat least one filler including a plurality of filler particles in thefiber stock suspension; and refining the fiber stock suspension aftersaid loading step to produce said plurality of filler particles in apredetermined size range.
 22. The method of claim 21, further includingthe step of producing the fiber web in a predetermined colorcorresponding to said predetermined size range.
 23. The method of claim21, wherein said refining step is a beating operation.
 24. A method fora production of a fiber web from a fiber stock suspension including afiller, comprising the steps of: loading at least one filler including aplurality of filler particles in the fiber stock suspension; and addingat least one dispersing chemical to the fiber stock suspension.
 25. Themethod of claim 24, further including the step of producing the fiberweb.
 26. The method of claim 25, further including the step of improvingat least one of an opacity of the fiber web and a brightness of thefiber web.